Several organization indices have been used to predict the outcome of stepwise catheter ablation (step-CA) in long-standing persistent atrial fibrillation (LS-pAF), however with limited success. Our study aims at developing innovative indices from baseline (BL) ECG (i.e before ablation) in order to predict the procedure outcome and the site of AF termination (AF-term) by step-CA. We report an adaptive method for tracking AF-term based on indices characterizing the relationship between harmonic components of atrial activity from the ECG. Our preliminary results suggest that adaptive measures of AF organization computed at BL perform better than classical indices for identifying patients whose AF will terminate during ablation within the left atrium only. These findings are indicative of a higher baseline organization in these patients.